Flatbed scanners
Flatbed scanners that first became affordable around the mid 1990’s can be divided into two types. Contact image Sensor (CIS) scanners use a range of red, blue and green LED’s that reflect light off the original that is then gathered by a sensor array. Charged Coupled Device (CCD) scanners use a light source, again refected off the original that is directed by mirrors to a sensor consisting of light capturing CCD elements. Both have advantages and disadvantages although CCD technology is generally recognised as having greater depth of field and signal noise ration and is used in the majority of modern flatbeds.